Plants annual; tufted. Culms 20-90 cm, sometimes decumbent, often
with many branches arising from the base. Sheaths strongly compressed-keeled;
ligules 0.6-1.8 mm; blades 4-27 cm long, 1.5-5(7.5) mm wide,
adaxial surfaces scabrous or sparsely pilose. Panicles 1.5-8(10) cm; fascicles
8.3-11.9 mm long, 3.5-6 mm wide, somewhat globose, medium- to short-pubescent;
bristles 45-75; outer bristles numerous, shorter and thinner than
the inner bristles, imbricate, mostly terete, reflexed; inner bristles
3.5-7 mm long, 0.5-0.9(1.4) mm wide at the base, irregularly placed, fused for
1/2 their length or more, forming a distinct cupule, the distal portions diverging
at irregular intervals from the cupule, often grooved along the margins, purple-tinged.
Spikelets 2-3(4) per fascicle, (4)5.8-7.8 mm. Lower glumes 0.8-3
mm; upper glumes 4-6 mm, 3-5-veined; lower florets often staminate;
lower lemmas 4-6.5 mm, 3-7-veined; anthers 1.5-2 mm; upper lemmas
4-7(7.6) mm; anthers 0.7-1 mm, seemingly not well-developed at anthesis.
Caryopses 2-3.8 mm long, 1.5-2.6 mm wide, ovoid. 2n = 34 (38).
Cenchrus longispinus grows in sandy woods, fields, and waste ground in
southern Canada and the contiguous United States. Its range extends southwards
to Venezuela. It is often confused with C. spinifex
and C. tribuloides; see discussion
under those species.
Spreading or ascending annual 2-8 dm, usually branched; sheaths villous-ciliate distally; blades 6-18 cm נ3-7 mm; burs hairy, 8-12 נ3.5-6 mm (spines excluded), with numerous (mostly 45-75) retrorsely barbed, slender spines 3.5-7 mm, the lower spines relatively short and pointed downward; spikelets 2-3(4) per bur, 6-8 mm, exserted at the tip, visible down to the middle through the lateral cleft in the bur; 2n=34. A weed in sandy soil or disturbed habitats; Me. to Fla., w. to N.D., Oreg., Calif. and Tex.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.